Add events to your Google Calendar by sending it a tweet. All you have to do is authorize your account on their website, follow gcal on Twitter, and send direct messages to it using Google’s Quick Add syntax, and presto!

Someone else should try this out to see if it’s any good since I don’t use Google Calendar.

Send a text message to Twitter (short code 40404) with the message “track <blank>” to get updates anytime <blank> is mentioned in the Public Timeline. To stop getting updates, text back “untrack <blank>”

Create folksonomies by tagging your tweets for personal organization and public consumption using the pound sign (hash mark). Add #<tag> anywhere in the tweet and it will get posted to the Hashtags website under that tag. Chris Messina has proposed a whole hashtag syntax that would group your tweets on your Twitter homepage, but it has yet to be implemented.

Hashtags were popularized during last year’s forest fires in San Diego. Once a tag is widely agreed upon (in this case, #sandiegofire), it can be used to aggregate tweets from people across the world, giving us one central location to track important updates. This could be incredibly useful if paired with Twitter Track. More recently #macworld was used for MacWorld Expo.

Note: I’ve sent four or five tweets with hashtags in them, but they don’t seem to updating to the hashtag website. Is there typically a delay this long or is something down? [Update: eight hours later, it’s working. There must have been a glitch in the system]

This one I’m particularly excited about. Follow rtm on Twitter to add tasks via direct message. First you’ll have to authorize access to your account, send a sort of Captscha direct message to rtm, and wait for a response. Then you’re all set to send tasks using a simple syntax. To get the full list: d rtm !tips

You can even set up tweet reminders so that it’s all contained in one little app — which you’re already staring at all day.

Here’s what I did today:

Once I sent the message, it automatically appeared in my Remember the Milk inbox. How cool!

I’m sure I’ll continue to discover more great uses of Twitter and you know I’ll pass them along.